07/15/2004 Env Bd Packet - Laserfiche WebLink

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• • 9:00 a.m. to 5:00 p.m. Saturday; no work on Sundays or holidays. Sound levels can be monitored and if the maximum level is exceeded, adjustments can be made to the methods being used. The other aspect of the pile driving activity is the potential for impacts from vibration. If the project proceeds, the City will require a pre - construction survey and monitoring program based on specifications used by MnDOT. The specifics would need to be determined further, but the program would include elements such as: 1. A pre - construction building survey within 100 feet of the project to document the existing exterior and interior conditions 2. Crack displacement monitoring gauges to help verify distress if any should develop 3. Continuously recording seismographs 4. Submittal of a plan identifying schedule, vibration, equipment, and monitoring log 5. Records of construction location, hours worked, depth, and equipment generating the vibrations 6. Submittal of construction logs weekly including complaints 7. A test program prior to beginning activities to demonstrate the requirements can be met 8. Sound levels should not exceed 90 decibels measured at 50 feet 9. Maximum vibration levels could be established. If these limits are exceeded, the contractor would have to cease the activity exceeding the limit and design corrective action. 10. In addition to these elements, a reasonable financial security could be established to repair any damage to existing structures. This could involve third party arbitration to determine the fairness of a claim and the appropriate remedy. Such a program would establish requirements to protect existing structures and means to enforce the requirements. While the above list represents a reasonable approach, it may be appropriate to adjust the specifics of these requirements depending on specific equipment, additional soils information, the new bridge design, or other information. Water Quality Impacts Some impact on water quality will occur with the dewatering and other activities as part of construction of the bridge. The original design reviewed by the DNR for bridge permit approval showed five piers. Although approved, the design was later revised to show one pier and two 150 -foot spans. The most recent five -pier design will require additional fill and construction dewatering. These impacts will be temporary. A "preservation area" has been incorporated into the stormwater plan. This area is located on the north side of the island. Because it is downhill from the building sites, flow control and water quality are enhanced by flow dispersion through duff, undisturbed soils, and native vegetation. The preserved area will be clearly marked during clearing and construction on the site. The project approval can include a mechanism to protect this area such as covenants or a conservation easement. Erosion control measures will be implemented during construction in accordance with the Best Management Practices contained in the MPCA Stormwater Construction Permit program to DRAFT July 1, 2004 Pheasant Hills Preserve 12th Addn. EAW Record of Decision page 4